Display device

ABSTRACT

In a device for displaying images by application of an electric field to a charged substance, a structure for reducing afterimages and a method for manufacturing the structure are provided. The device is a display device which includes a plurality of pixel electrodes and a charged layer (a layer including a charged substance) provided over the pixel electrodes. An end of one of two pixel electrodes that are adjacent to each other among the plurality of pixel electrodes has a depression in an end-face direction, and an end of the other of the pixel electrodes has a projection in the end-face direction. In a state in which the depression and the projection are in a set, a gap is formed between the two pixel electrodes.

This application is a continuation of copending U.S. application Ser.No. 14/618,418, filed on Feb. 10, 2015 which is a continuation of U.S.application Ser. No. 14/335,306, filed on Jul. 18, 2014 (now U.S. Pat.No. 8,958,140 issued Feb. 17, 2015) which is a continuation of U.S.application Ser. No. 13/168,025, filed on Jun. 24, 2011 (now U.S. Pat.No. 8,786,934 issued Jul. 22, 2014), which are all incorporated hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The technical field of the present invention relates to a display deviceand a method for driving a display device. Further, the technical fieldof the present invention relates to a method for manufacturing a displaydevice.

2. Description of the Related Art

These days, with the development of digitization techniques, text dataand image data of newspapers, magazines, and the like can be provided aselectronic data. This kind of electronic data is generally displayed ona display device included in a television, a personal computer, aportable electronic terminal, or the like, so that the content of thedata can be read.

As display devices with high visibility equivalent to the visibility ofpaper, display devices using electronic ink such as electrophoreticelements have been developed. As a display device using electronic ink,for example, there is a display device which includes a microcapsulebetween a pixel electrode and a counter electrode. In such a displaydevice, images are displayed by application of voltage between the twoelectrodes and movement of colored particles in the microcapsule in anelectric field direction (see Reference 1).

REFERENCE

Reference 1: Japanese Published Patent Application No. 2008-276153

SUMMARY OF THE INVENTION

In Reference 1, there has been a problem in that afterimages aregenerated when display images are switched.

One of the causes of the problem is that an end 5003 of a pixelelectrode 5001 is linear as illustrated in FIG. 13A. When the end 5003is linear, an electric field might be inadequately applied to a gap 5005between the pixel electrodes at the time of image display as illustratedin FIG. 13B; thus, afterimages are generated. Note that in the casewhere initialization treatment is performed in order to reduceafterimages, image display is slowed down.

In view of the problem, it is an object to improve the performance of adisplay device, for example, to reduce afterimages.

A display device disclosed in this specification is a device fordisplaying images by application of an electric field to a chargedsubstance. When the display device includes a plurality of pixelelectrodes and some or all of the ends of two pixel electrodes that areadjacent to each other are nonlinear, an electric field is adequatelyapplied to the charged substance in a gap between the pixel electrodes.

One embodiment of the present invention is a display device whichincludes a plurality of pixel electrodes and a charged layer (alsoreferred to as a layer including a charged substance) provided over thepixel electrodes. Ends of two pixel electrodes that are adjacent to eachother among the plurality of pixel electrodes include curved portions inan end-face direction. In this specification, the end-face direction isa direction that is parallel to an upper surface of the pixel electrode.In addition, the curved portion may have a shape with a vertex (alsoreferred to as an angular shape) or a shape without a vertex (alsoreferred to as a bent shape). Further, the curved portions of the twopixels electrodes are preferably engaged with each other.

Another embodiment of the present invention is a display device whichincludes a plurality of pixel electrodes and a charged layer providedover the pixel electrodes. Between two pixel electrodes that areadjacent to each other among the plurality of pixel electrodes, an endof one of the pixel electrodes has a depression (or a depression and aprojection) in an end-face direction, and an end of the other of thepixel electrodes has a projection (or a depression and a projection) inthe end-face direction. In a state in which the depression (or thedepression and the projection) of the one of the pixel electrodes andthe projection (or the depression and the projection) of the other ofthe pixel electrodes are in a set, a gap is formed between the two pixelelectrodes. In this specification, the description “a depression and aprojection (or depressions and projections) are in a set” means a statein which the projection fits in the depression. Further, this state maybe expressed by description “a depression and a projection are engagedwith each other”.

Another embodiment of the present invention is a display device whichincludes a plurality of pixel electrodes and a charged layer providedover the pixel electrodes. A gap is formed between two pixel electrodesthat are adjacent to each other among the plurality of pixel electrodes.The gap has three or more portions whose distances are equal to eachother. In the three or more portions, when the middle points of thedistances are connected with segments, one or more vertexes areobtained.

Another embodiment of the present invention is a display device whichincludes a plurality of pixel electrodes and a charged layer providedover the pixel electrodes. Between two pixel electrodes that areadjacent to each other among the plurality of pixel electrodes, ends ofthe two pixel electrodes are curved and a gap is formed. The gap hasthree or more portions whose distances are equal to each other.

Another embodiment of the present invention is a display device whichincludes a plurality of pixel electrodes and a charged layer providedover the pixel electrodes. A right end of one of the plurality of pixelelectrodes and a left end of a pixel electrode that is adjacent to theright side of the one pixel electrode are curved and a gap is formed. Anupper end of the one pixel electrode and a lower end of a pixelelectrode that is adjacent to the upper side of the one pixel electrodeare curved and a gap is formed. The gap in the right side of the onepixel electrode and the gap in the upper side of the one pixel electrodehave two or more portions whose distances are equal to each other.

Thus, it is possible to improve the performance of a display device, forexample, to reduce afterimages.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 illustrates an example of a display device;

FIG. 2 illustrates an example of the display device;

FIG. 3 illustrates an example of the display device;

FIG. 4 illustrates an example of the display device;

FIG. 5 illustrates an example of the display device;

FIG. 6 illustrates an example of the display device;

FIGS. 7A to 7D each illustrate an example of a display device;

FIGS. 8A and 8B each illustrate an example of a display device;

FIGS. 9A and 9B each illustrate an example of a display device;

FIGS. 10A to 10E illustrate an example of a display device;

FIG. 11 illustrates an example of the display device;

FIGS. 12A to 12F each illustrate an example of an electronic device; and

FIGS. 13A and 13B illustrate an example of a conventional displaydevice.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described in detail below with reference to thedrawings. Note that the embodiments can be implemented in variousdifferent ways. It will be readily appreciated by those skilled in theart that modes and details of the embodiments can be modified in variousways without departing from the spirit and scope of the presentinvention. The present invention therefore should not be construed asbeing limited to the following description of the embodiments. In allthe drawings for describing the embodiments, the same portions orportions having similar functions are denoted by the same referencenumerals, and description thereof is not repeated.

(Embodiment 1)

In this embodiment, structure examples of a display device aredescribed.

FIG. 1 is a top view of a pixel portion in a display device. Note thatFIG. 1 illustrates part of the pixel portion.

The pixel portion includes a plurality of pixels. The plurality ofpixels each include a pixel electrode 101. In one embodiment of thepresent invention, part of an end of the pixel electrode 101 or theentire end of the pixel electrode 101 is nonlinear. That is, the end ofthe pixel electrode 101 includes a portion 103 that is curved in anend-face direction. Note that the end of the pixel electrode 101 mayinclude a linear portion 105. Further, the curved portions 103 and 104of the adjacent two pixel electrodes 101 are preferably engaged witheach other.

Here, detailed conditions of the structure of the pixel electrode 101are described with reference to FIG. 2, FIG. 3, FIG. 4, and FIG. 5 thatare magnified views of FIG. 1.

First, a first condition is described. Between two pixel electrodes thatare adjacent to each other, an end of one of the pixel electrodes has adepression in the end-face direction, and an end of the other of thepixel electrodes has a projection in the end-face direction. Thedepression of the one of the pixel electrodes and the projection of theother of the pixel electrodes are in a set, and a gap is formed betweenthe two pixel electrodes. Ends of the two pixel electrodes havedepressions and projections, and the depression and projection of theone of the pixel electrodes and the depression and projection of theother of the pixel electrodes may be in a set.

FIG. 2 illustrates a specific example of the first condition. A pixelelectrode 201 includes depressions 211 and a projection 213. A pixelelectrode 203 includes a depression 215 and projections 217. Thedepression 211 of the pixel electrode 201 and the projection 217 of thepixel electrode 203 are in a set, and the projection 213 of the pixelelectrode 201 and the depression 215 of the pixel electrode 203 are in aset. That is, the depressions and projection of the pixel electrode 201and the depression and projections of the pixel electrode 203 are insets, and a gap 219 is formed between the two pixel electrodes 201 and203. With the first condition, the projecting portion 103 of the pixelelectrode illustrated in FIG. 1 is formed.

In addition, a second condition is described. A gap is formed betweentwo pixel electrodes that are adjacent to each other. The gap has threeor more portions whose distances are equal to each other. In the threeor more portions, when the middle points of the distances are connectedwith segments, one or more vertexes are obtained. That is, the middlepoints of the distances in the three or more portions are not arrangedin a straight line.

FIG. 3 illustrates a specific example of the second condition. The gap219 is formed between the two pixel electrodes 201 and 203 that areadjacent to each other. The gap 219 has three portions 301, 303, and 305whose distances are equal to each other. In the three portions, when themiddle points of the distances are connected with segments, one vertex307 is obtained. With the second condition, the projecting portion 103of the pixel electrode illustrated in FIG. 1 is formed.

In addition, a third condition is described. Between two pixelelectrodes that are adjacent to each other, ends of the two pixelelectrodes are curved and a gap is formed. The gap has three or moreportions whose distances are equal to each other. In particular, thedistances of the portions in half or more of one side of each of the twopixel electrodes are preferably equal to each other.

FIG. 4 illustrates a specific example of the third condition. Ends 401and 403 of the two pixel electrodes 201 and 203 are curved and the gap219 is formed. The distance of the gap 219 is uniform in one sides ofthe pixel electrodes. With the third condition, the projecting portion103 of the pixel electrode illustrated in FIG. 1 is formed.

In addition, a fourth condition is described. A right end of one pixelelectrode and a left end of a pixel electrode that is adjacent to aright side of the one pixel electrode are curved and a gap is formedbetween the ends. An upper end of the one pixel electrode and a lowerend of a pixel electrode that is adjacent to an upper side of the onepixel electrode are curved and a gap is formed between the ends. The gapin the right side of the one pixel electrode and the gap in the upperside of the one pixel electrode have two or more portions whosedistances are equal to each other.

FIG. 5 illustrates a specific example of the fourth condition. A rightend 501 of the pixel electrode 201 and a left end 502 of the pixelelectrode 203 are curved and the gap 219 is formed therebetween. Anupper end 503 of the pixel electrode 201 and a lower end 504 of a pixelelectrode 205 are curved and a gap 221 is formed therebetween. The gap219 and the gap 221 have two portions 505 and 507 whose distances areequal to each other. With the fourth condition, the projecting portion103 of the pixel electrode illustrated in FIG. 1 is formed.

Note that in the above conditions, the description “distances are equalto each other” includes the case where distances are substantially equalto each other in consideration of errors.

Advantageous effects of the structures of the pixel electrodes aredescribed below.

FIG. 6 is a cross-sectional view of the pixel portion in FIG. 1, whichillustrates three pixels. Further, FIG. 6 illustrates an example where amicrocapsule electrophoretic element is used as a display element.

One pixel includes a display element 601 which includes a pixelelectrode 603, a counter electrode 605, and a charged layer 606 (alsoreferred to as a layer including a charged substance) provided betweenthe pixel electrode 603 and the counter electrode 605. A pixel that isadjacent to the one pixel includes the display element 601 whichincludes a pixel electrode 609 adjacent to the pixel electrode 603, thecounter electrode 605, and the charged layer 606.

The charged layer 606 includes a plurality of microcapsules 607. Themicrocapsule 607 includes colored particles 623 and 625. The coloredparticles 623 and 625 function as charged substances.

In addition, a gap 611 is formed between the pixel electrode 603 and thepixel electrode 609.

Any of the structures of the pixel electrodes that are illustrated inFIG. 1, FIG. 2, FIG. 3, FIG. 4, and FIG. 5 is used as the structures ofthe pixel electrodes 603 and 609. Thus, in the gap 611 in FIG. 6, thepixel electrode 603 includes a projecting portion 613 in the depthdirection of paper. The projecting portion 613 corresponds to theportion 103 in FIG. 1, the projection 213 in FIG. 2, and the like.

When voltage is applied between the pixel electrodes 603 and 609 and thecounter electrode 605 in this state, electric fields are generated asindicated by arrows 615.

Since an electric field is also generated in the projecting portion 613of the pixel electrode 603, an electric field can be applied to theparticles 623 and 625 adequately also in part of the gap 611 or theentire gap 611. Consequently, afterimages generated in the gap 5005 inthe conventional display device in FIGS. 13A and 13B can be reduced.

Note that the distance of the gap 611 is preferably smaller than a gap(also referred to as a cell gap) between the pixel electrode 603 and thecounter electrode 605.

An example of the charged layer 606 is described in detail below.

The charged layer 606 includes the plurality of microcapsules 607 and aresin 617. The microcapsules 607 are dispersed in and fixed to the resin617. The resin 617 functions as a binder.

The resin 617 preferably has light-transmitting properties. Instead ofthe resin 617, the charged layer 606 may be filled with a gas such asair or an inert gas. In that case, a layer or layers containing anadhesive or the like may be formed on either one or both the pixelelectrode 603 and the counter electrode 605 so that the microcapsules607 are fixed.

The microcapsule 607 includes a film 619, a liquid 621, the particle623, and the particle 625. The liquid 621, the particle 623, and theparticle 625 are encapsulated in the film 619. The film 619 haslight-transmitting properties. The cross-sectional shape of themicrocapsule 607 is not limited to a round shape, and may be anelliptical shape or an uneven shape.

The liquid 621 functions as a dispersion liquid. The liquid 621 candisperse the particle 623 and the particle 625 in the film 619. Notethat it is preferable that the liquid 621 have light-transmittingproperties and be non-tinted.

The particle 623 and the particle 625 have different colors. Forexample, one of the particle 623 and the particle 625 may be black andthe other of the particle 623 and the particle 625 may be white. Notethat the particle 623 and the particle 625 are charged so as to havedifferent electrical charge densities, and function as chargedsubstances. For example, one of the particle 623 and the particle 625may be charged positively and the other of the particle 623 and theparticle 625 may be charged negatively. Thus, a potential difference isgenerated between the pixel electrode 603 and the counter electrode 605,and the particle 623 and the particle 625 move in accordance with thedirection of an electric field. Accordingly, the reflectance of thedisplay element 601 is changed, so that gradation can be controlled.

Note that the structure of the microcapsule 607 is not limited to theabove structure. For example, the liquid 621 may be colored. Inaddition, the colors of the particles can be selected from red, green,blue, cyan, magenta, yellow, emerald green, vermillion, or the like inaddition to white and black. Further, the colors of the particles may beone kind of color or three or more kinds of colors.

Further, the mode of the display element 601 is not limited to amicrocapsule type. A microcup type, a horizontal movement type, avertical movement type, a twisting ball type (e.g., a spherical twistingball or a cylindrical twisting ball), a powder movement type, anelectronic liquid powder (registered trademark) type, a charged toner,electro wetting, electrochromism, electrodeposition, or the like can beapplied to the display element 601. The display element 601 correspondsto all the elements that can be used for image display by movement ofcharged substances such as particles included in the charged layer 606.

Note that in the case where a display image is viewed from the counterelectrode 605 side, the counter electrode 605 is formed using alight-transmitting material. As the light-transmitting material, it ispossible to use, for example, indium tin oxide (ITO), indium tin oxidecontaining silicon oxide (ITSO), organoindium, organotin, zinc oxide(ZnO), indium zinc oxide (IZO), zinc oxide containing gallium, tin oxide(SnO₂), indium oxide containing tungsten oxide, indium zinc oxidecontaining tungsten oxide, indium oxide containing titanium oxide, orindium tin oxide containing titanium oxide.

In that case, the pixel electrode 603 can be formed using thelight-transmitting material or a metal material. In particular, thepixel electrode 603 is preferably formed using a metal material whosereflectance of visible light is low or a metal material whoseabsorptance of visible light is high. When the pixel electrode 603 isformed using such a material, reflectance on the pixel electrode 603does not easily occur; thus, visibility of the display image isimproved. As a metal whose reflectance is low, for example, chromium orthe like can be used.

Alternatively, the display image may be viewed from the pixel electrode603 side. In that case, the pixel electrode 603 is formed using thelight-transmitting material.

In that case, the counter electrode 605 is preferably formed using ametal whose reflectance is lower than the reflectance of the metal usedfor the pixel electrode 603. The counter electrode 605 can be formedusing the metal whose reflectance is low.

Alternatively, the display image may be viewed from the counterelectrode 605 side and the pixel electrode 603 side. In that case, thecounter electrode 605 and the pixel electrode 603 are formed using thelight-transmitting material. In order to prevent light from shiningthrough opposite sides, polarizing plates are preferably provided on thecounter electrode 605 side and the pixel electrode 603 side in crossednicols.

This embodiment can be combined with any of the other embodiments asappropriate.

(Embodiment 2)

In this embodiment, structure examples of pixel electrodes that aredifferent from the example in FIG. 1 are described.

FIGS. 7A to 7D are top views of pixel portions in display devices. Notethat FIGS. 7A to 7D illustrate some of the pixel portions.

In FIG. 7A, the pixel portion includes a pixel electrode 701. An end ofthe pixel electrode 701 includes a rectangular projecting portion in anend-face direction.

In FIG. 7B, the pixel portion includes a pixel electrode 703. An end ofthe pixel electrode 703 includes a trapezoidal projecting portion in anend-face direction.

In FIG. 7C, the pixel portion includes a pixel electrode 705. An end ofthe pixel electrode 705 includes a triangular projecting portion in anend-face direction.

In FIG. 7D, the pixel portion includes a pixel electrode 707. A rightend of the pixel electrode 707 includes a triangular projecting portionin an end-face direction. An upper end of the pixel electrode 707includes a projecting portion in the end-face direction.

Even in the case where any of the structures in FIGS. 7A to 7D isemployed, an electric field can be applied to a gap between two pixelelectrodes that are adjacent to each other as in FIG. 1, FIG. 2, FIG. 3,FIG. 4, FIG. 5, and FIG. 6 when any of the first to fourth conditionsdescribed in Embodiment 1 is satisfied. Thus, afterimages in the gap canbe reduced.

Further, any of the structures in FIG. 1, FIG. 7A, FIG. 7B, FIG. 7C, andFIG. 7D may be used in combination.

This embodiment can be combined with any of the other embodiments asappropriate.

(Embodiment 3)

In this embodiment, structure examples of display devices are described.

FIGS. 8A and 8B each illustrate examples of pixel circuits and drivercircuits. FIG. 8A illustrates a passive-matrix display device, and FIG.8B illustrates an active-matrix display device. Each display deviceincludes the display elements 601 in a plurality of pixels 801 arrangedin matrix.

The structure of the display element that is described in the aboveembodiment can be used as the structure of the display element and adriving method.

In the passive-matrix display device illustrated in FIG. 8A, the pixel801 includes a plurality of crossed wirings 803 and 805 and the displayelement 601 which is electrically connected to the crossed wirings 803and 805. In addition, the wiring 803 is electrically connected to adriver circuit 811, and the wiring 805 is electrically connected to adriver circuit 813. Further, the display element 601 expresses gradationin accordance with potentials input from the driver circuit 811 and thedriver circuit 813.

In the active-matrix display device illustrated in FIG. 8B, the pixel801 includes the plurality of crossed wirings 803 and 805, a transistor807, the display element 601, and a capacitor 809. A gate of thetransistor 807 is electrically connected to the wiring 805. One of asource and a drain of the transistor 807 is electrically connected tothe wiring 803. The other of the source and the drain of the transistor807 is electrically connected to the display element 601 and thecapacitor 809. In addition, the wiring 803 is electrically connected tothe driver circuit 811, and the wiring 805 is electrically connected tothe driver circuit 813. On and off of the transistor 807 are controlledin accordance with a potential input from the driver circuit 813.Further, the display element 601 expresses gradation in accordance witha potential input from the driver circuit 811 at the time when thetransistor 807 is on. Note that the capacitor 809 has a function ofholding voltage applied to the display element 601.

Next, cross-sectional structures of pixel portions are described.

FIG. 9A illustrates a cross-sectional structure of the passive-matrixdisplay device. The display element 601 is provided between a substrate901 and a counter substrate 903. The plurality of wirings 803illustrated in FIG. 8A are the pixel electrodes 603 and 609 on thesubstrate 901 side extended in a direction perpendicular to paper. Thus,it is preferable that any of the first to third conditions is satisfiedat ends of the plurality of wirings 803 that serve as the pixelelectrodes 603 and 609. The plurality of wirings 805 illustrated in FIG.8A are the counter electrode 605 on the counter substrate 903 sideextended in a direction parallel to the paper. Note that although FIG.9A illustrates only one counter electrode 605, the plurality of counterelectrodes 605 are provided in the direction parallel to the paper. Thatis, the display elements 601 are formed in portions where the pluralityof wirings 803 and the plurality of wirings 805 intersect with eachother.

FIG. 9B illustrates a cross-sectional structure of the active-matrixdisplay device. A layer containing the transistor 807 and the capacitor809 and the display element 601 formed over the layer are providedbetween the substrate 901 and the counter substrate 903. In addition,the transistor 807 and the capacitor 809 are electrically connected tothe pixel electrode 603. Note that although not illustrated in FIG. 9B,a transistor and a capacitor are electrically connected to the pixelelectrode 609.

As the substrate 901 and the counter substrate 903, a glass substrate, aresin substrate, a semiconductor substrate, a metal substrate, or any ofthe substrates provided with an insulating film such as a nitride filmor an oxide film can be used as appropriate.

The transistor 807 is a bottom-gate thin film transistor, which includesan electrode 911, an insulating film 913, an electrode 915, an electrode917, and a semiconductor layer 919. Here, the electrode 911 is a gateelectrode. In addition, the insulating film 913 is a gate insulatingfilm. Further, one of the electrode 915 and the electrode 917 functionsas a source electrode, and the other of the electrode 915 and theelectrode 917 functions as a drain electrode.

The capacitor 809 includes an electrode 921, the electrode 917, and theinsulating film 913. Here, the electrode 921 is a lower electrode of thecapacitor 809 and a conductive layer that is formed in the same layer asthe electrode 911 (the gate electrode). In addition, the insulating film913 functions as the gate insulating film and a dielectric of thecapacitor 809. Further, the electrode 917 is a conductive layer extendedover the insulating film 913 and functions as one of the sourceelectrode and the drain electrode and an upper electrode of thecapacitor 809.

The electrode 911, the electrode 921, the electrode 915, and theelectrode 917 are each formed to have a single-layer structure or alayered structure of a metal material such as molybdenum, titanium,tantalum, tungsten, aluminum, copper, neodymium, or scandium or an alloymaterial containing the metal material as a main component.

The insulating film 913 is formed as a single layer or stacked layers ofa silicon oxide film, a silicon nitride film, or the like.

The semiconductor layer 919 can be formed using an amorphoussemiconductor, a polycrystalline semiconductor, a single crystalsemiconductor, or a microcrystalline semiconductor. In addition, as thematerial of the semiconductor, silicon, germanium, an organicsemiconductor, an oxide semiconductor, or the like can be used. Further,either a p-channel transistor or an n-channel transistor may be used.Note that either a channel-etched transistor or a channel-stoptransistor may be used, and a top-gate structure may be employed.Furthermore, a transistor using a semiconductor substrate (also referredto as a bulk transistor) may be used instead of a thin film transistor.

The transistor 807 can have a variety of structures such as asingle-drain structure, an LDD (lightly doped drain) structure, and agate-overlap drain structure.

Further, an insulating film 923 is formed between the transistor 807 andthe capacitor 809, and the pixel electrode 603.

The insulating film 923 has a single-layer structure or a layeredstructure of an inorganic material such as silicon oxide or siliconnitride, an organic material such as polyimide, polyamide,benzocyclobutene, acrylic, or epoxy, a siloxane material, or the like.

Furthermore, a structure in which a color filter (CF) or a black matrix(BM) is provided on the substrate 901 side or the counter substrate 903side may be employed as appropriate, for example. Note that CFs or BMsmay be provided on both the substrate 901 side and the counter substrate903 side.

This embodiment can be combined with any of the other embodiments asappropriate.

(Embodiment 4)

In this embodiment, examples of methods for manufacturing displaydevices are described. Note that the structures described in the aboveembodiment can be used as appropriate as materials, structures, and thelike.

First, a method for manufacturing the passive-matrix display device isdescribed with reference to FIG. 9A.

Wirings which serve as the pixel electrodes 603 and 609 are formed overthe substrate 901 so as to extend in a direction perpendicular to paper.Here, a conductive film which serves as the pixel electrodes isdeposited, and then, is subjected to etching or the like and isprocessed into the pixel electrodes 603 and 609 so that any of the firstto third conditions is satisfied.

Next, the charged layer 606 (also referred to as the layer including acharged substance) is formed over the pixel electrodes 603 and 609. Forexample, the resin 617 where the microcapsules 607 are dispersed andfixed is provided over the pixel electrodes 603 and 609.

Then, a wiring which serves as the counter electrode 605 is formed overthe resin 617 (the charged layer 606) so as to extend in a directionparallel to the paper. Note that the resin 617 over which the counterelectrode 605 is fowled in advance may be provided over the pixelelectrodes 603 and 609.

Next, the counter substrate 903 is provided over the counter electrode605. The counter substrate 903 is attached to the substrate 901 with asealant.

Note that the counter substrate 903 on which the counter electrode 605is formed may be attached to the substrate 901 with a sealant.

In the case where electronic liquid powder is used instead of themicrocapsules, a polymer micro-particle which is positively charged andcolored with a certain color and a polymer micro-particle which isnegatively charged and colored with a different color may be providedbetween the pixel electrode 603 and the counter electrode 605. In thismanner, the display element can be formed by the different method.

Thus, the passive-matrix display device can be manufactured.

Next, a method for manufacturing the active-matrix display device isdescribed with reference to FIG. 9B. Description of steps that aresimilar to the steps in the passive-matrix display device is omitted.

The transistor 807 and the capacitor 809 are formed over the substrate901.

The insulating film 923 is formed over the transistor 807 and thecapacitor 809.

The pixel electrodes 603 and 609 are formed over the insulating film923. Here, a conductive film which serves as the pixel electrodes isdeposited, and then, is subjected to etching or the like and isprocessed into the pixel electrodes 603 and 609 so that any of the firstto fourth conditions is satisfied.

Next, the charged layer 606 (also referred to as the layer including acharged substance) is formed over the pixel electrodes 603 and 609. Forexample, the resin 617 where the microcapsules 607 are dispersed andfixed is provided over the pixel electrodes 603 and 609.

Then, the counter electrode 605 is formed over the resin 617 (thecharged layer 606). Note that the resin 617 over which the counterelectrode 605 is formed in advance may be provided over the pixelelectrodes 603 and 609.

Next, the counter substrate 903 is provided over the counter electrode605. The counter substrate 903 is attached to the substrate 901 with asealant.

Note that the counter substrate 903 on which the counter electrode 605is formed may be attached to the substrate 901 with a sealant.

Thus, the active-matrix display device can be manufactured.

This embodiment can be combined with any of the other embodiments asappropriate.

(Embodiment 5)

In this embodiment, an example of a method for manufacturing a displaydevice that is different from the example in Embodiment 4 is described.Note that the structures described in the above embodiment can be usedas appropriate as materials, structures, and the like.

First, a separation layer 931 is formed over the substrate 901 (see FIG.10A).

The separation layer 931 can be formed to have a single-layer structureor a layered structure of a material such as tungsten, molybdenum,titanium, tantalum, niobium, nickel, cobalt, zirconium, zinc, ruthenium,rhodium, palladium, osmium, iridium, or silicon. Alternatively, theseparation layer 931 may be formed using an alloy material containingsuch an element as a main component, or a compound material containingsuch an element as a main component. The separation layer 931 can beformed to a thickness of 30 to 200 nm with the use of such a material bysputtering, plasma-enhanced CVD, coating, printing, or the like.

In addition, an insulating film (e.g., a silicon nitride film or asilicon oxide film) which serves as a buffer layer may be formed overthe separation layer 931. Provision of the insulating film facilitatesseparation along a surface of the separation layer 931 in a laterseparation step.

Next, the pixel electrodes 603 and 609 are formed over the separationlayer 931. Here, a conductive film which serves as the pixel electrodesis deposited, and then, is subjected to etching or the like and isprocessed into the pixel electrodes 603 and 609 so that any of the firstto fourth conditions is satisfied.

An insulating film 933 is formed over the pixel electrodes 603 and 609.The insulating film 933 has a single-layer structure or a layeredstructure of an inorganic material such as silicon oxide or siliconnitride, an organic material such as polyimide, polyamide,benzocyclobutene, acrylic, or epoxy, a siloxane material, or the like.The insulating film 933 can be formed using such a material by CVD,sputtering, an SOG method, a droplet discharge method, screen printing,or the like.

Then, the transistor 807 and the capacitor 809 are formed over theinsulating film 933. In addition, the transistor 807 and the capacitor809 are electrically connected to the pixel electrode 603. Note that atransistor and a capacitor which are electrically connected to the pixelelectrode 609 are not illustrated in FIG. 10A.

After that, parts of the insulating film 933 that are provided at endsof the substrate 901 are removed by etching or the like. Then, aninsulating film 935 is formed so as to cover the transistor 807 and thecapacitor 809. The insulating film 935 functions as a barrier layer andcan be formed using a nitrogen-containing layer (a layer containingsilicon nitride, silicon nitride oxide, silicon oxynitride, or thelike).

Next, grooves 937 are formed by irradiation of the insulating film 935with laser beams (see FIG. 10B). Then, a separate film 939 is providedso as to cover at least the grooves 937 (see FIG. 10C).

After that, a first organic resin 941 is formed over the insulating film935. Provision of the separate film 939 can prevent the first organicresin 941 from entering the grooves 937 and being bonded to theseparation layer 931. Note that the organic resin 941 functions as asubstrate (also referred to as a support substrate).

Then, an element layer 943 is separated from the substrate 901 along thesurface of the separation layer 931 from the grooves 937 (see FIG. 10D).The separate film 939 is eliminated after the separation.

Next, as described in another embodiment, the charged layer 606 (thelayer including a charged substance) is formed over the pixel electrodes603 and 609 (see FIG. 10E). Note that the separated element layer 943 isused while being upside down.

Then, a second organic resin 945 on which the counter electrode 605 isformed is provided over the charged layer 606. After that, the firstorganic resin 941 and the second organic resin 945 are bonded to eachother by heat treatment. The second organic resin 945 functions as acounter substrate.

Note that the formation order of the charged layer 606, the counterelectrode 605, and the counter substrate may be similar to the formationorder in the above embodiment.

A thermosetting resin such as an epoxy resin, an unsaturated polyesterresin, a polyimide resin, a bismaleimide-triazine resin, or a cyanateresin can be used as the first organic resin 941 and the second organicresin 945. Alternatively, a thermoplastic resin such as a polyphenyleneoxide resin, a polyetherimide resin, or a fluorine resin may be used. Aflexible display device can be manufactured using an organic resin.

Note that a passive-matrix display device can be manufactured byapplying the manufacturing method.

This embodiment can be combined with any of the other embodiments asappropriate.

(Embodiment 6)

In this embodiment, the positional relation between a pixel electrodeand different wirings is described.

FIG. 11 illustrates an example of the positional relation between thepixel electrode illustrated in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5,or FIG. 6 and the wirings 803 and 805 illustrated in FIG. 8B.

In FIG. 11, the pixel electrode 201 and the wirings 803 and 805 overlapwith each other. That is, the wiring 803 does not overlap with a gap 950and the wiring 805 does not overlap with a gap 960.

With this positional relation, in the gap 950, an electric fieldgenerated by the potential of the wiring 803 can be prevented from beingapplied to a charged substance. Thus, afterimages can be reduced in thegap 950.

Similarly, in the gap 960, an electric field generated by the potentialof the wiring 805 can be prevented from being applied to a chargedsubstance. Thus, afterimages can be reduced in the gap 960.

This embodiment can be combined with any of the other embodiments asappropriate.

(Embodiment 7)

In this embodiment, examples of electronic devices are described.

FIGS. 12A and 12B each illustrate electronic paper (also referred to asan e-book reader, an electronic book, or the like). In FIGS. 12A and12B, the display device disclosed in this specification can be used in adisplay portion 4101 in a main body 4001 and a display portion 4102 in amain body 4002.

Further, without limitation to the electronic paper, the display devicedisclosed in this specification can be used in display portions 4103 to4106 in main bodies 4003 to 4006 in electronic devices such as atelevision in FIG. 12C, a cellular phone in FIG. 12D, a personalcomputer in FIG. 12E, and a game machine in FIG. 12F.

This embodiment can be combined with any of the other embodiments asappropriate.

This application is based on Japanese Patent Application serial No.2010-144911 filed with Japan Patent Office on Jun. 25, 2010, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A display device comprising a display portion,the display portion comprising: an element layer comprising a pluralityof transistors and a plurality of pixel electrodes, wherein each of theplurality of pixel electrodes overlaps with and is electricallyconnected to each of the plurality of transistors; a layer including acharged substance, the layer provided over the element layer; and acounter electrode over the plurality of pixel electrodes with the layerincluding the charged substance positioned therebetween, wherein each ofthe plurality of pixel electrodes has a first end, a second end beingadjacent to the first end, a third end being opposite to the first endand a fourth end being opposite to the second end, wherein among theplurality of pixel electrodes, first, second, and third pixel electrodesare arranged successively on one line, wherein each of the first ends ofat least the second and third pixel electrodes has a projection, andeach of the third ends of at least the first and second pixel electrodeshas a depression, and wherein the depression of the third end of thefirst pixel electrode and the projection of the first end of the secondpixel electrode are facing each other with a first gap positionedtherebetween, and the depression of the third end of the second pixelelectrode and the projection the first end of the third pixel electrodeare facing each other with a second gap positioned therebetween.
 2. Thedisplay device according to claim 1, wherein the layer including thecharged substance includes a plurality of microcapsules.
 3. The displaydevice according to claim 1, wherein the first, second, and third pixelelectrodes are arranged successively in a column direction.
 4. Thedisplay device according to claim 1, wherein the first, second, andthird pixel electrodes are arranged successively in a row direction. 5.The display device according to claim 1, wherein each of the second endsof at least one of the first, second, and third pixel electrodes has aprojection, and each of the fourth ends of at least the first and secondpixel electrodes has a depression.
 6. The display device according toclaim 1, wherein each of the first and second gaps includes three ormore portions whose distances are equal to each other.
 7. The displaydevice according to claim 6, wherein in the three or more portions, whenmiddle points of the distances are linked in a line, the line has one ormore vertexes.
 8. The display device according to claim 1, wherein theelement layer further comprises a substrate comprising resin.
 9. Thedisplay device according to claim 1, wherein the display device is apassive matrix display device.
 10. The display device according to claim1, wherein the display device is an active matrix display device. 11.The display device according to claim 1, wherein the display device isflexible.
 12. A display device comprising a display portion, the displayportion comprising: an element layer comprising a plurality oftransistors and a plurality of pixel electrodes, wherein each of theplurality of pixel electrodes overlaps with and is electricallyconnected to each of the plurality of transistors; a layer including acharged substance, the layer provided over the element layer; and acounter electrode over the plurality of pixel electrodes with the layerincluding the charged substance positioned therebetween, wherein each ofthe plurality of pixel electrodes has a first end, a second end beingadjacent to the first end, a third end being opposite to the first end,and a fourth end being opposite to the second end, wherein among theplurality of pixel electrodes, first, second, and third pixel electrodesare arranged successively on one line, wherein each of the first ends ofat least the second and third pixel electrodes has a first projectionand a first depression, and each of the third ends of at least the firstand second pixel electrodes has a second depression and a secondprojection, wherein the second depression of the third end of the firstpixel electrode and the first projection of the first end of the secondpixel electrode are facing each other with a first gap positionedtherebetween, and the second projection of the third end of the firstpixel electrode and the second depression of the first end of the secondpixel electrode are facing each other with the first gap positionedtherebetween, and wherein the second depression of the third end of thesecond pixel electrode and the first projection the first end of thethird pixel electrode are facing each other with a second gap positionedtherebetween, and the second projection of the third end of the secondpixel electrode and the second depression of the first end of the thirdpixel electrode are facing, each other with the second gap positionedtherebetween.
 13. The display device according to claim 12, wherein thelayer including the charged substance includes a plurality ofmicrocapsules.
 14. The display device according to claim 12, wherein thefirst, second, and third pixel electrodes are arranged successively in acolumn direction.
 15. The display device according to claim 12, whereinthe first, second, and third pixel electrodes are arranged successivelyin a row direction.
 16. The display device according to claim 12,wherein each of the second ends of at least one of the first, second,and third pixel electrodes has a third projection and a thirddepression, and each of the fourth ends of at least the first and secondpixel electrodes has a fourth depression and fourth projection.
 17. Thedisplay device according to claim 12, wherein each of the first andsecond gaps includes three or more portions whose distances are equal toeach other.
 18. The display device according to claim 17, wherein in thethree or more portions, when middle points of the distances are linkedin a line, the line has one or more vertexes.
 19. The display deviceaccording to claim 12, wherein the element layer further comprises asubstrate comprising resin.
 20. The display device according to claim12, wherein the display device is a passive matrix display device. 21.The display device according to claim 12, wherein the display device isan active matrix display device.
 22. The display device according toclaim 12, wherein the display device is flexible.
 23. A display devicecomprising a display portion, t he display portion comprising; anelement layer comprising a plurality of transistors and a plurality ofpixel electrodes, wherein each of the plurality of pixel electrodesoverlaps with and is electrically connected to each of the plurality oftransistors; a layer including a charged substance, the layer providedover the element layer; and a counter electrode over the plurality ofpixel electrodes with the layer including the charged substancepositioned therebetween, wherein each of the plurality of pixelelectrodes has a first end, a second end being adjacent to the firstend, a third end being opposite to the first end, and a fourth end beingopposite to the second end, wherein among the plurality of pixelelectrodes, first, second, and third pixel electrodes are arrangedsuccessively on one line, wherein each of the first ends of at least thesecond and third pixel electrodes has a first projection and a firstdepression, and each of the third ends of at least the first and secondpixel electrodes has a second depression and a second projection,wherein the second depression of the third end of the first pixelelectrode and the first projection of the first end of the second pixelelectrode are adjacent to each other with a first gap positionedtherebetween, and the second projection of the third end of the firstpixel electrode and the second depression of the first end of the secondpixel electrode are adjacent to each other with the first gap positionedtherebetween, and wherein the second depression of the third end of thesecond pixel electrode and the first projection the first end of thethird pixel electrode are adjacent to each other with a second gappositioned therebetween, and the second projection of the third end ofthe second pixel electrode and the second depression of the first end ofthe third pixel electrode are adjacent to each other with the second gappositioned therebetween.
 24. The display device according to claim 23,wherein the layer including the charged substance includes a pluralityof microcapsules.
 25. The display device according to claim 23, whereinthe first, second, and third pixel electrodes are arranged successivelyin a column direction.
 26. The display device according to claim 23,wherein the first, second, and third pixel electrodes are arrangedsuccessively in a row direction.
 27. The display device according toclaim 23, wherein each of the second ends of at least one of the first,second, and third pixel electrodes has a third projection and a thirddepression, and each of the fourth ends of at least the first and secondpixel electrodes has a fourth depression and fourth projection.
 28. Thedisplay device according to claim 23, wherein each of the first andsecond gaps includes three or more portions whose distances are equal toeach other.
 29. The display device according to claim 28, wherein in thethree or more portions, when middle points of the distances are linkedin a line, the line has one or more vertexes.
 30. The display deviceaccording to claim 23, wherein the element layer further comprises asubstrate comprising resin.
 31. The display device according to claim23, wherein the display device is a passive matrix display device. 32.The display device according to claim 23, wherein the display device isan active matrix display device.
 33. The display device according toclaim 23, wherein the display device is flexible.